1. Field of the Invention
The present invention relates to a liquid-encapsulated bushing including elastomeric members disposed between outer and inner sleeves having axes parallel to each other. A plurality of liquid chambers are defined to face the elastomeric members and to communicate with one another through orifices, so that the relative movement of the outer and inner sleeves is buffered by a resistance due to a liquid passing through the orifices.
2. Description of the Related Art
FIG. 8 shows a conventional liquid-encapsulated bushing. As can be seen in FIG. 8, the conventional liquid-encapsulated bushing B includes an outer sleeve 01 and an inner sleeve 02 having an axis L. A liquid chamber R.sub.5 and a liquid chamber R.sub.6 are defined by the outer sleeve 01, first elastomeric member 04 which interconnects a collar 03 fitted over an outer periphery of the inner sleeve 02 and by a pair of second elastomeric members 06 which are coupled to the outer sleeve 01 through spacers 05. The liquid chambers R.sub.5 and R.sub.6 are connected to each other by two orifices O.sub.5.
When the first elastomeric member 04 is deformed by a load to cause the outer and inner sleeves 01 and 02 to be relatively moved in directions of arrows X and X', the volumes of the liquid chambers R.sub.5 and R.sub.6 are alternately increased and decreased. The liquid in the liquid chambers R.sub.5 and R.sub.6 flows between the liquid chambers R.sub.6 and R.sub.5 through the orifices O.sub.5. Thus, the load is buffered by a resistance, due to the liquid, generated during the flowing of the liquid. When a further larger load is input to cause the outer and inner sleeves 01 and 02 to be moved largely relative to each other, the first elastomeric member 04 is brought into close contact with one of the second elastomeric members 06, thereby inhibiting the increase in amount of relative movement of the outer and inner sleeves 01 and 02 to exhibit a stopper function.
FIG. 9 is a graph illustrating the characteristic of the amount of relative movement produced between the outer and inner sleeves 01 and 02 of the liquid-encapsulated bushing B provided at the end of the suspension arm, when a tire of a vehicle runs over an uneven road surface. If a load in a direction X, which is a longitudinal direction of the suspension arm, is input, the amount of relative displacement of the outer and inner sleeves 01 and 02 in the direction X is gradually increased (see areas a and b). If the amount of relative displacement in the direction X approaches a limit, the outer and inner sleeves 01 and 02 are displaced relative to each other in a direction Z which is perpendicular to the direction X by a load component which cannot be absorbed (see area c).
The conventional liquid-encapsulated bushing is effective for damping of loads in the directions X and X', but suffers from a problem that loads in the directions Z and Z', perpendicular to the directions X and X', cannot be damped effectively.